There is traditionally much demand for oily foods represented by chocolate in the market, and recently there are a variety of oily foods for meeting marketing needs that accompany diversification of tastes. In particular, there is a high demand for an oily food having good meltability in the mouth and a novel texture in the market.
On the other hand, in an oily food, generally, when meltability in the mouth is improved, heat resistance is decreased. Therefore, for recent merchandise which may be frequently exposed to variable temperatures and environments in a distribution process, it is important to have stronger resistance to heat as well as good meltability in the mouth.
A representative fat for chocolate is mainly cocoa butter. A chocolate containing much cocoa butter is rapidly softened or deformed at a high temperature of 28° C. or more, and thereby its commercial value is remarkably decreased.
For this reason, various attempts to improve the heat resistance of an oily food have ever been made and, inter alia, a method of modifying a fat has been generally used frequently.
Fat contains triacylglycerols (hereinafter, referred to as TG) as the main component and, inter alia, cocoa butter contains symmetric TGs as the main component. A symmetric TG refers to a TG in which saturated fatty acids are bound to the 1,3-positions and an unsaturated fatty acid is bound to the 2-position, and when a large amount of symmetric TGs are contained in a fat, an oily food having good meltability in the mouth is obtained by performing solidification of the fat under strict temperature control and manipulation (said temperature manipulation is called “tempering”, and a fat containing a large amount of symmetric TGs which requires such a tempering procedure is referred to as a “tempering-type fat”).
Of such a type of oily foods, the most common oily food is a chocolate which contains cocoa butter as the main raw material. Cocoa butter contains symmetric TGs, particularly, 1,3-distearoyl-2-oleoyl-glycerol (hereinafter, referred to as StOSt), 1,3-dipalmitoyl-glycerol (hereinafter, referred to as POP) and 2-oleoyl-stearoylpalmitoylglycerol (hereinafter, referred to as POS) in large amounts. Among symmetric triglycerides which are the main component of cocoa butter, a TG having the highest melting point is StOSt (1,3-distearoyl-2-oleoylglycerin). A method of increasing the heat resistance of an oily food which comprises adding a fat rich in StOSt has been widely used (see, for example, Gerard Hogenbirk, “Compatibility of Specialty Fats with Cocoa Butter”, The Manufacturing Confectioner, 1984 (5), pp. 59-64, Toshiharu Arishima, “Applications of Specialty fats and Oils”, The Manufacturing Confectioner, June 2002, pp. 65-76, JP-A 49-9507, pp. 1-33).
When the content of StOSt in a fat is increased to heighten the melting point, the heat resistance is increased, and however, at the same time, the meltability of the fat in the mouth is greatly deteriorated. Particularly, since a chocolate containing a large amount of symmetric TGs gains excellent taste and meltability in the mouth via solidification under strict temperature manipulation (tempering), it is not desirable that the valuable meltability in the mouth is sacrificed for increase in heat resistance.
Thus, in the market, there is a strong need for a method of increasing heat resistance and minimizing deterioration in the meltability in the mouth of an oily food.